The present invention relates to cationically modified polyurethane (urea) masses which have very high water absorption capacities. These masses are in the form of lumps or sheets (preferably in the form of lumps) and contain prefinished foams, and optionally other fillers, in particular lignite dust, magnetite and/or peat, which are bound in the polyurethane (urea) masses in an abrasion resistant form.
It is known that the preparation of materials of the type mentioned above can be carried out by the reaction of cationically modified isocyanate prepolymers having a functionality above 2.1 with a stoichiometric excess quantity of water in the presence of size reduced, prefinished foams, in particular PU foams. It is preferred to also add lignite powder, magnetite and/or peat, optionally other inorganic or organic fillers and optionally biomasses (living cells, living bacteria, enzymes).
The polyurethane(urea) masses in question contain up to 95% by weight of fillers of prefinished foam particles and optionally other fillers and at least 5% by weight of polyurethane (urea) matrix. The masses are already swelled with water and have a high water content as the result of the method of preparation.
According to the present state of the art, e.g. as disclosed in U.S. Pat. Nos. 4,608,397, 4,734,439, 4,801,621 and 4,855,052 (which correspond to European patents 151,937 and 151,938), the water absorption capacity when suspended in water is from 33 to 97% by weight of water.
The binders preferably used in U.S. Pat. No. 4,734,439, 4,801,621 and 4,855,052 are cationically modified isocyanate prepolymers, which are preferably derived from i) polyethers, ii) compounds containing tertiary nitrogen (e.g. N-methyl-diethanolamine), iii) quaternizing agents (dimethyl sulphate, polyphosphoric acid) and iv) diisocyanates (e.g a mixture of 2,4- and 2,6-diisocyanatoluene). The resulting ionically modified isocyanate prepolymers contain the ionic particles in a finely dispersed form, as evidenced by the white color of the prepolymer. The conditions employed for their preparation must be observed very accurately since the dispersed particles would otherwise tend to sediment due to their large size. The dispersion would therefore have a limited storage stability. The quality of the polyurethane-(urea) masses, and in particular the abrasion resistance of the bound fillers, is adversely affected if the particles of isocyanate prepolymer are too coarse.